I have done some other tests. I have the same problem on a clean install of 18.04 with Displaylink 5.3 but Displaylink 5.2 can be installed without trouble. Libdrm-dev seems to have been updated very recently. I think this is the problem and that's why the driver can't be installed anymore on a clean install. I can't suceed to install the previous version of the libdrm-dev package but maybe it can solve the problem.